The central role of the Genetic Susceptibility Testing Core is to provide a resource for BRCA1 mutation testing, to develop and maintain the Duke Familial Breast Cancer Database (FBCD), and develop and maintain a DNA bank within the Duke Breast Cancer SPORE. This will provide a resource for genetic epidemiologic and molecular studies at Duke University Medical Center. The overall goal of this effort is to advance our basic and clinical understanding of the BRCA1 susceptibility gene for breast cancer. This goal is accomplished by providing key personnel to assemble breast cancer family data, to collect blood samples for molecular analyses, and to sequence DNA to determine the presence of BRCA1 mutations. The Genetic Susceptibility Testing Core will directly interface with Drs.Winer's and Rimer's study and will provide the resource to identify relatives from familial breast-ovarian cancer families. The Genetic Susceptibility Testing Core will also provide BRCA1 sequencing capabilities for Drs. Mark's and Berchuck's study of the molecular biology and function of the BRCA1 gene. Data will be generated to facilitate Drs. Berry's and Prosnitz's effort in developing decision models. All statistical analyses will be performed by the Biostatistics and Data Management Core. The Genetic Susceptibility Testing Core will not only provide a resource for the various SPORE-related projects but will be a spring-board for future genetic epidemiologic and molecular studies of familial breast cancer. We will also collaborate with Dr. Steven Narod and participate in the activities of the North American Breast Cancer Consortium.